Method of making compact conductor

ABSTRACT

Improved electrical conductor is formed by compacting concentric conductors which have outside wires with gages at least equal to the gages of the inside wires. Such a conductor with 37 or more wires may have the outer layer only made up of square wires.

United states Patent 1191 1111 3,823,542 Pemberton [4 July 16, 1974 METHOD OF MAKING COMPACT [56] References Cited CONDUCTOR UNITED STATES PATENTS [7 5] .lnventor: Denver L. Pemberton, Fairmount, 1,943,087 1/1934 Potter et a1. 57/161 X 1nd. 3,164,670 1/1965 34,722 66 [73] Assigneez The Anaconda Company, New 96,522 33 York, NY 3,444,684 5/1969 Schoerner 57/161 [22] Filed: May 24, 1973 P E D Id E W k rimary xaminer ona at ins [21] Appl' N05 363,683 Attorney, Agent, or Firm-Victor 1F. Volk Related US. Application Data [621 Division of Ser. No. 244,083, April 14, 1972, Pat. ABSTRACT 31760093' Improved electrical conductor is formed by compacting concentric conductors which have outside wires Ef-il. with gages at least equal to the gages of the inside 0 0 1 4 4 i 4 n i [58] Field of Search 57/55, 9, 138, 145, 156, Wes Such a conductor or more Wes may have the outer layer only made up of square wires.

2 Claims, 3 Drawing Figures PATENTED JUL 1 si n a w v This is a division of application Ser. No. 244,083 filed Apr. 14, 1972, now U.S. Pat. No. 3,760,093.

BACKGROUND OF THE INVENTION The conductors of electric cables are customarily made by stranding together a plurality of wires in concentric layers. The geometry of the cable cross section is naturally such that six wires will fit firmly around a single center wire, 12 wires will fit around the six, 18 wires around the 12, etc. each layer having six more wires than the underlying layer. Conductors made up in this manner are known as concentric lay conductors and are described in a number of industry standards, such as American Society for Testing Materials (ASTM) E 8-70. The number of wires in such aconcentric lay conductor will equal exactly 311 3n l where n represents the number of layers surrounding the central wire. Concentric lay conductors, however, have large overall diameters for a given conductance, or cross section of metal, caused by the many open spaces or interstices between the wires. To reduce the conductor diameter it has been known to crush or compact the wires after the layers have been applied, so as to force some of the metal into the interstices. Conductors with wires so crushed are known as compact round conductors. U.S. Pat. No. 1,943,087, which issued in 1934, is still fairly representative of the state of the art of compact round conductors and a number of industry standards, such as ASTM B 496-69 describe them. Compacting of a standard conductor, however, changes the geometrical dimensional relationships so that a layer with six more wires than the underlying layer no longer fits naturally onto the conductor. The aforementioned compact conductor patent teaches, and the teaching has been generally followed in commerce, that, to compensate for the reduction in diameter of the conductor core by compacting, the individual diameters of wires in succeeding layers should be reduced. This has had the significant manufacturing advantage that all the reel carriers of the stranding machines are utilized, but it has also had the serious disadvantage that many different wire sizes are required to be drawn and stocked. Another disadvantageous practice of the known art of making compact round conductors, as followed in commerce, and as taught by the early patent, has been the necessity to reduce the length of stranding lay substantially below the maxi mum allowed by ASTM and other industry standards. This is 16 times the diameter for copper (see ASTM E 496-69) and for Class B strand aluminum (see ASTM B 400-70). Shortening of the lay adds significantly to the cost of manufacturing since it reduces the hourly production of the stranding machines.

The aforementioned patent taught the art of compacting conductors by means of pressure rolls. More recently it has been known that it is also feasible to effect the compacting by pulling the conductor through a wire drawing type die after the application of each layer of wires, but conductors made by either method, using industry teachings for the selection of wire sizes and lay lengths, have been characterized by wide variations of temper, due to uneven work hardening, through the conductor section. Typically, the more central wires have been excessively hardened. When such conductors are flexed or tensioned the load is not 2 evenly distributed and failure will occur earlier than it would for a conductor of uniform hardness throughout its section.

SUMMARY I have invented a new compact electrical cable conductor and method that reduces the number of different wire sizes to be drawn and permits a maximum stranding lay for each layer. My conductor has a reduced diameter for a given conductance and a relatively uniform degree of work hardening in each layer. Copper conductor, compacted to my invention, has retained an elongation averaging over percent in each layer, although the diameter is reduced even below that of prior art conductors in which some wires retained elongations of less than 5 percent. My present conductor comprises a central wire and a plurality of layers of helically applied wires surrounding the central wire. An

innermost of these layers consists of six wires and each additional layer comprises a plurality of wires six in number greater than the number of wires in the directly underlying layer. The gage of the individual wires in any layer of my conductor is not less than the gage of any underlying wire and the conductor is compacted to a diameter at least 8 percent less than the diameter of a concentric lay conductor of equal circular mil area. Embodiments of my conductor comprise constructions wherein the central wire and all the wires in the layers are round and of the same gage before compacting, and constructions of three or more layers wherein the wires of the outermost layer, only, are square and of a larger gage. In preferred embodiments the wires in my conductorcomprise copper and the layers alternate in direction of lay.

My method for making acompact conductor for an electric cable consisting of 3m 3n 1 wires helically wound in n layers over a central of said wires comprises steps of continuously pulling the central wire from a supply thereof through n fixed, linearly mounted, wire drawing type dies, pulling six round wires, of a sectional area at least as large as the sectional area of the central wire from supplies of the same being driven in rotation around the central wire, through a first of the dies, and therein forming a compacted core from the wires. This first die has a minimum aperture no greater than 92 percent of 3 times the diameter of the central wire. In my method I also pull twelve round wires each having a sectional area at least as large as the sectional area of one of the six wires, from supplies driven in rotation around the core through a second of the dies therein compacting the wires and enlarging the core. This second die has a minimum aperture no greater than 92 percent of 5 times the diameter of the central wire. For each of any additional layers l pull a plurality of wires six in number greater than the number of wires in the next underlying layer through one of the plurality of dies having a minumum aperture no larger than 92 percent of (2m 1) times the diameter of the central wire where m represents the layer number. Each of these additional layer wires is at least as large in sectional area as any of the underlying wires and is pulled from supplies being driven in rotation around the core.

BRIEF DESCRlPTlON OF THE DRAWING FIG. 11 shows a section of a conductor of my invention.

FIG. 2 shows a section of another embodiment of the conductor of my invention.

FIG. 3 shows steps in the method ofmy invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS As seen in FIG. 1, a compact conductor of my invention indicated by the numeral has a central wire 11 surrounded by three layers 12, 13, 14 of wire wrapped helically around it. Prior to compacting, the wire 11 and all the wires of the layers l2-14 are round. FIG. 2 shows another embodiment of my conductor differing from that of FIG. 1 by having an outside layer 16 of square wires. An essential feature wherein my conductors differ from prior compact round conductors resides in the fact that the wires of the outer layers 14, 16 are no smaller in cross-section or gage than the wire 11. Beneficially, all the round wires are the same gage. To form the conductor 10 the central wire 11, along with six identical wires of the layer 12, are pulled through a wire drawing type die 17 which compresses or compacts the strand at least 8 percent, creating the sectional appearance of FIGS. 1 and 2, wherein the interstices between the wires have been substantially filled with metal by deforming the initial circular shape of both the wire 11 and the wires of the layer 12. The die 17 and downstream dies 18, 19, 21 to be further described are mounted rigidly in line and the wires are pulled through the dies at a predetermined rate by capstan means, not shown, associated with a stranding machine such as a type of machine known as a rigid strander on which six reels holding supplies of the wires ofthe layer 12 are rotated around the line of the central wire 11 as the wires are pulled off into the die 17. In a like manner, but in the opposite direction of rotation, 12 round wires of the layer 13 are rotated around a compacted core 22 being pulled into the die 18. 18 wires of the layer 14 are rotated to apply a left hand lay into the die 19 completing the conductor 10. The method of FIG. 3 can be applied to an indefinite number of layers as shall be further explained with examples hereinbelow. l have shown the application of an additional layer of 24 wires 23 of the same size as the wire 11 through a wire drawing type die 21 with a right hand lay. It is a feature of my invention that a superior compact conductor can be formed of copper wires with the direction of lay alternated to balance the construction. ASTM B 49669, the industry standard for compact round copper conductors has followed the teaching of the US. Pat. No. 1,943,087 that the layers should all have the same direction of lay and my invention, involving the application of full size wires or larger in the outer layers also has advantages for such a unilay construction. It should be noted that ASTM B 400-70, for aluminum compact round conductors has permitted the alternation of layers, presumably because of the softer metal. Example 1, below, typifies a copper conductor made from round wires in accordance with my invention.

EXAMPLE 1 Conductor size, 500 MCM, 37 wires Diameter of each of the round wires, inch, 0.1247

Aperture of die 17 over six wires, inch, 0.316

Length and direction of lay of six wires, 4.74 inches Aperture of die 18 over 12 wires, inch, 0.526

Length and direction of lay of 12 wires, 7.89 inches,

Aperture of die 19 over 18 wires, inch, 0.736

Length and direction of lay of 18 wires, 1 1.04 inches,

A detailed consideration of EXAMPLE 1 will clarify some of the features of my invention. The total number of wires are 37 and the number of layers over the central wire are three. This corresponds to the formula for a concentric strand, S 3n 3n 1, where n represents the number of layers and S the number of wires. The diameter over the second layer of an uncompacted strand would be (2m l times the wire diameter with m equal to two or, 5 X 0.1247 0.6235 inch, the pitch diameter of the next layer would equal 0.6235 0.1247 equals 0.7482 inch. An eighteen sided polygon inscribed in a circle of this diameter would have a perimeter of 18 X 0.7482 X sin 10= 2.326 inches. The sum of the diameters of 18 strands of 0. 1 247 inch wires equals 2.245 inches, allowing the 18 strands to fit an uncompacted core with an allowance for the lay angle. In the compacted core of EXAMPLE 1 however, the die 19 has an aperture of only 0.736 inch, if we obtain the pitch diameter by subtracting one wire diameter (0. 1247) from this aperture we obtain 0.61 13 inch. An eighteen sided polygon inscribed in a 0.61 13 inch circle will have a perimeter of only 18 X 0.61 13 X sin 10 1.9107 inches. Since, as has been stated, the eighteen wires require a perimeter of 2.245 inches, they must be crushed together even before entering the die 19. l have found, surprisingly, that it is not only possible to introduce wires of this large diameter, but that so doing produces a more compact conductor and one in which there is no excessive work hardening.

EXAMPLE 2 Conductor size, Awg No. 1/0, 19 wires Diameter of each round wire, 0.0817 inch Aperture of die 17 over six wires, 0.204 inch Lay of six wires, 3.24 inches R.H.

Aperture of die 18 over 12 wires, 0.340 inch Lay of 12 wires, 5.31 inches L.H.

EXAMPLE 3 Conductor size, Awg No. 2/0, 19 wires Diameter of each round wire, 0.0915 inch Aperture of die over six wires, 0.229 inch Lay of six wires, 3.47 inches R.H. Aperture of die over 12 wires, 0.382 inch Lay of 12 wires, 5.93 inches L.H.

EXAMPLE 4 Conductor size, Awg No. 4/0, 19 wires Diameter of each round wire, 0.1 153 inch Aperture of die over six wires, 0.288 inch Lay of six wires, 4.06 inches R.H. Aperture of die over 12 wires, 0.480 inch Lay of 12 wires, 7.61 inches L.H.

EXAMPLE 5 Conductor size, 750 MCM, 61 wires Diameter of each round round wire, 0.1215 inch Aperture of die over six wires, 0.302 inch Lay of six wires, 4.53 inches, R.H.

Aperture of die over 12 wires, 0.503 inch Lay of twelve wires, 7.55 inches L.H.

Aperture of die over 18 wires, 0.705 inch Lay of 18 wires, 10.58 inches R.H.

Aperture of die over 24 wires, 0.906 inch Lay of 24 wires 13.59 inches, L.H.

I have found that where there are three or more layers over the central wire an increased surface smoothness of the conductor and a lessening of the pulling load of the stranding machine can be achieved by drawing the wires in the outer layer square, instead of round. The same number of wires are used in the layer as would be used for a conventional concentric strand i.e. 6m wires, where m represents the number of layers, and the sectional area of the square wire is at least as great as any of the other wires in the conductor, in fact, I prefer to increase the area in the square wires as illustrated in EXAMPLES 6-10 below.

EXAMPLE 6 Side of square wires 0.0794 inch, area 0.005961 in Aperture of die over 18 square wires, 0.522 inch Lay of 18 wires 8.04 inches, L.H. deducted for rounded corners per ASTM B 48-68 The square wire layer is compacted at least 8 percent by the wire drawing type die as are the round wires of all my novel conductors. Thus, considering the conductor of EXAMPLE 6, the diameter of the 12 wire die is 0.380 inch. Over this is applied a layer of square wires 0.0794 inch on a side which would increase the diameter of the core to 0.5378 inch. But the final die is only 0.522 inch, permitting a radial increase of only 0.071 inch instead of 0.0794. These teachings will also be seen to apply to the EXAMPLES following.

EXAMPLE 7 Conductor size, 350 MCM, 37 wires Diameter of each round wire, 0.1010 inch Die aperture over six wires, 0.270 inch Die aperture over 12 wires, 0.450 inch Lay of 12 wires, 6.90 inches, R.H.

Side of square wires 0.0940 inch Die aperture over 18 square wires 0.616 inch Lay of square wires, 9.57 inches, L.H.

EXAMPLE 8 Conductor size, 500 MCM, 37 wires Diameter of each round wire, 0.1210 inch Die aperture over six wires, 0.325 inch Die aperture over 12 wires 0.540 inch Lay of 12 wires, 8.06 inches R.H.

Side of square wires 0.1 120 inch Die aperture over 18 square wires 0.736 inch Lay of square wires 1 1.02 inches, L.H.

EXAMPLE 9 Conductor size, 750 MCM, 61 wires Diameter of each round wire, 0.1 153 inch Aperture of die over six wires, 0.307 inch Aperture of die over 12 wires, 0.512 inch Aperture of die over 18 wires, 0.717 inch Lay of 18 wires 10.57 inches, R.H.

Side of square wires 0.1060 inch Lay of 24 square wires 14.16 inches L.H. Die aperture over square wires, 0.906 inch EXAMPLE 10 Conductor size 1000 MCM, 61 wires Diameter of each round wire, 0.1330 inch Aperture of die over six wires, 0.358 inch Aperture of die over 12 wires, 0.597 inch Aperture of die over 18 wires, 0.836 inch Lay of 18 wires, 12.34 inches R.H.

Side of square wires, 0.1225 inch Die aperture over 24 wires, 1.056 inches Lay of square wires 16.40 inches L.H.

in addition to the benefits of high production speeds and lower diameters already mentioned, 1 have found that running compact round conductors with large out side wires has the unexpected result that the strand remains tight on the strander capstan during reel changes, can be stranded without adding oil for lubricant, and gives excellent die wear.

The dies 117, 18, 119, 21 differ from commonly used wire drawing dies in having larger apertures but they are characterized with wire drawing dies in being formed of tungsten carbide or material of similar hardness, having highly polished smooth inner surfaces, widened entrance zones 1011, cylindrical or substantially cylindrical lands 1102, and, preferably, conical reliefs W3.

1 have invented a new and useful compact round c0nductor for electric cables, and a new method of making such conductor of which the foregoing description has been exemplary rather than definitive and for which 1 desire an award of Letters Patent as defined in the following claims.

1 claim:

1. The method of making a compact conductor for an electric cable consisting of 3n 3n 1 wires helically wound in n layers over a central of said wires comprising the steps of:

. A. continuously pulling said central wire from a supply thereof through n fixed, linearly mounted dies,

B. pulling six round wires, of a sectional area at least as large as the sectional area of said central wire from supplied of the same driven in rotation around said central wire, through a first of said dies, therein forming a compacted core from said wires, said first die having a minimum aperture no greater than 92 percent of 3 times the diameter of said central wire,

C. pulling 12 round wires of a sectional area at least as large as the sectional areas of said six wires from supplies of the same driven in rotation around said core through a second of said dies therein compacting said wires and enlarging said core, said second die having a minimum aperture no greater than 92 percent of 5 times the diameter of said central wire,

D. for each of any additional layers, pulling a plurality of wires six in number greater than the number of wires in the next underlying layer, each said additional layer wire being at least as large in sectional area as any of the underlying wires, from supplies of said wires driven in rotation around said core through one of said plurality of dies having a minimum aperture no larger than 92 percent of (2m 1) times the diameter of said central wire, where m represents the layer number, and therein compacting said wires.

2. The method of claim 1 wherein the supplies of wires in alternate layers rotate in opposite directions. =i i I UNITED STATES PATENT OFFICE @ERTIFICATE OF CORRECTION Patent No 3 ,B2.3,542 Dated JULY 16, 1974 Kim/encode) DENVER L. PEMBER'ION It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cancel "supplied" and insert Claim 1, Column 6, Line 42 supplies-.

Signed and sealed this 5th day of November 1974.

(SEAL) Attest:

McCOY M, GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (IO-69) uscoMM-oc oosvmpon I I U.S. GOVERNMENT PRINTING OFFICE l9" O-Jll-SSO.

V UNITED STATES PATENT OFFICE ERTIFICATE OF CORRECTION Dated JULY 16 1974 Patent No. 3 823 542 lnvenmfle) DENVER L. PEMBERTON hove-identified patent It is certified that error appears in the a d as shown below:

and that said Letters Patent are hereby correcte Cancel "supplied? and insert Claim 1, Column 6, Line 42 -supplies.

Signed and sealed this 5th day of November 1974.

(SEAL) Attest:

McCOY Me GIBSON JR. C. MARSHALL DANN Commissioner of Patents Atteating Officer R ($59) uscoMM-Dc wan-Poe Q U.S, GOVIRN'IINY 'IIITING OI'FIC! l I... O 1."33" 

1. The method of making a compact conductor for an electric cable consisting of 3n2 + 3n + 1 wires helically wound in n layers over a central of said wires comprising the steps of: A. continuously pulling said central wire from a supply thereof through n fixed, linearly mounted dies, B. pulling six round wires, of a sectional area at least as large as the sectional area of said central wire from supplied of the same driven in rotation around said central wire, through a firSt of said dies, therein forming a compacted core from said wires, said first die having a minimum aperture no greater than 92 percent of 3 times the diameter of said central wire, C. pulling 12 round wires of a sectional area at least as large as the sectional areas of said six wires from supplies of the same driven in rotation around said core through a second of said dies therein compacting said wires and enlarging said core, said second die having a minimum aperture no greater than 92 percent of 5 times the diameter of said central wire, D. for each of any additional layers, pulling a plurality of wires six in number greater than the number of wires in the next underlying layer, each said additional layer wire being at least as large in sectional area as any of the underlying wires, from supplies of said wires driven in rotation around said core through one of said plurality of dies having a minimum aperture no larger than 92 percent of (2m + 1) times the diameter of said central wire, where m represents the layer number, and therein compacting said wires.
 2. The method of claim 1 wherein the supplies of wires in alternate layers rotate in opposite directions. 